Switchable terahertz absorber based on vanadium dioxide for bandwidth tunable broadband absorption and four-band absorption

We propose a switchable metamaterial absorber (MMA) for bandwidth tunable broadband and four-band absorption in the terahertz (THz) band based on the phase-transition characteristics of vanadium dioxide (VO2). The proposed MMA can achieve over 90% broadband absorption in the 3.06-7.61, 3.18-8.91, and 2.78-9.22 THz ranges when the conductivity of VO2 is 3x10(5), 3x10(4), and 2x10(4) S m(-1), respectively, and has the advantages of polarization insensitivity and wide-angle absorption. When VO2 is in the insulator phase, the MMA can achieve four-band high absorption, and the absorptance can reach 99% at 2.23, 4.06, 5.80, and 9.82 THz. Through the joint action of the multi-layer structure, the proposed MMA solves the problem that when only VO2 is used to tune the broadband absorption, the decrease in the conductivity of VO2 by 1 order of magnitude will lead to the obvious decrease in the broadband absorption bandwidth. A switchable absorber designed by a simple tuning method without changing the structure has significant development prospects in stealth technology and selective thermal emitters.